Another Norcold fridge question

[TitanTn]

I have a 1998 400 Express with the factory Norcold fridge. I don't have the exact model number yet. I know several people will give me an answer of "get a new fridge! Vitrifrigo and others. I might be headed there, but I want to identify my exact problem before I just go buy a new fridge.

The fridge is working on both AC and DC - not sure that it's super cold, but I haven't run it long enough to know for sure. The issue is that the fridge trips the shore power on my whole dock. When I'm running it on AC, it trips the power. When attempting DC, I can have the switch on the fridge itself turned off, but flipping on the DC refrigerator switch in the master panel it will trip the dock. I don't even have to turn on the dial on the front of the fridge.

Our dock has a sensitive ground fault protection system. I can't run my fridge at the dock. It will run on battery power when I'm not connected and it will run off the generator.

Any ideas on what the issue might be?

 

[mjoplin]

One possible scenario for you. Anytime you have an appliance that requires a sudden large load to start (refrigerator compressor), that sudden change can cause EMI (electro magnetic interference) that can trigger an overly sensitive GFCI (in this case on your dock).

I can see why it wouldn't cause issues on genset or battery power. You don't have that sensitive GFCI in the mix.

The description of your issue confounds me a bit.

If I read you correctly, when connected to shore power at the dock the frig will start up in AC mode, but trip the shore power breaker. Does it trip immediately when the compressor tries to cycle? That could possibly be EMI tripping the GFCI on the shore power unit.

The DC scenario as I read it: You (1) start with the on-board AC breaker shut off to the frig and the boat still on shore power. You (2) have the frig turned off (dial all the way off). You (3) flip the DC breaker to the frig on and the shore power is immediately tripped.

This is the one that troubles me. You have no compressor load on the frig starting up, you have simply energized the DC power supply. It should be drawing minimal current off your battery bank, the only connection back to shore power is via the on-board battery charger, which would be running off shore power AC.

You might try putting a big electrolytic capacitor across the input power to the frig as a transient decoupling capacitor. I did that on mine on the DC side mainly to buffer the initial draw as the compressor spools up. Not quite a snubber circuit, but might buffer enough EMI to help.

Another possibility, and maybe the simpler one, is a bad GFCI on the shore power unit. You might try plugging into a different one to see if you get the same results. They do go bad, a humid environment is hard on circuitry.

 

[TitanTn]

Thanks mjoplin. You're absolutely correct on my DC issue. To clarify the AC side, I have the fridge dial turned off, connect shore power, turn on the 120volt breakers in the panel (everything is still fine at this point), and then when I turn the dial on the fridge it immediately pops the main breaker on the dock.

But you're right about it being strange because this has nothing to do with the compressor starting up. It's just energizing the fridge circuit that will trip the dock.

I understand the concept of a capacitor, but I have no idea that type, size, or location for installing one in this scenario. I would also think this would primarily help as a dampener on the initial compressor startup but not necessarily a ground fault issue like this one. Not sure.

I haven't tried a different power pedestal, but I will. That's an easy check, but since everything electrical is fairly new on this dock, I'm betting it's something in the circuitry in my boat.

 

[mjoplin]

Good luck with it. I don't remember the size cap I have in there (and would have to pull the frig out to see). Something around a 30 uf or better should be sufficient. Only other thing I could suggest is looking at the ground connections. Maybe bonding it out to a solid ground might help. Odd that just energizing the ac/dc and dc/dc power supplies would trip the GFCI.

 

[TitanTn]

I just want to close the loop on this issue for anyone that might be searching this forum for a similar answer. My issue ended up being the circuit board on top of the fridge. Not sure exactly what it was, but I took it to a local electronics repair shop and they rebuilt it for $150. Everything seems to work as it should both on AC and DC and it doesn't trip my the ground fault on my dock. Very relieved to have it fixed and that it didn't require a new fridge.

 

[tdschafer]

I just want to close the loop on this issue for anyone that might be searching this forum for a similar answer. My issue ended up being the circuit board on top of the fridge. Not sure exactly what it was, but I took it to a local electronics repair shop and they rebuilt it for $150. Everything seems to work as it should both on AC and DC and it doesn't trip my the ground fault on my dock. Very relieved to have it fixed and that it didn't require a new fridge.

Thanks for the update! Glad it worked out inexpensively for you! It was nice of you to post the "Final Answer" for others down the road!

 

[Little Ducky]

WOW good news.

Post up the info for the local electronic shop..... if I ever need one I'll look them up.

 

[TitanTn]

WOW good news.

Post up the info for the local electronic shop..... if I ever need one I'll look them up.

Sure thing. It's MRO just off of Amnicola Hwy. I'd link to their web site but it's down for some reason. Decent sized operation that does circuit board and electrical motor rebuilds for companies all over the US.

 

[Little Ducky]

Sure thing. It's MRO just off of Amnicola Hwy. I'd link to their web site but it's down for some reason. Decent sized operation that does circuit board and electrical motor rebuilds for companies all over the US.

Good find. I have an old instrument cluster from my 88 VW that needs some TLC. The little electronic transistor thingy part is still available but I would hate to melt the plastic ribbon its soldered to if I did a DIY fix.